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Packaging of food products is one of the most important stages of the food supply chain. Nano-size materials for packing food substances with appropriate properties result in better packaging performance and longer food shelf-life. In this review, the application of ZnO nano-size in active packaging of foods is discussed to identify gaps in applications for food packaging and safety. First, the crystal structures and morphologies of modified ZnO nanoparticles (ZnO NPs) are presented, and their synergistic effects on antimicrobial activities are discussed. This review also provides an overview of antimicrobial packaging containing ZnO NPs with a focus on preparation methods, antimicrobial mechanisms, and recent progress in packaging applications. The generation of reactive oxygen species (ROS) is the primary antimicrobial mechanism, which can be varied depending on morphology and size. Generally, ZnO NPs can inactivate fungi or Gram-positive and Gram-negative bacteria growth, which reduce the risk of cross-contamination, thereby extending the shelf life of products. Notably, the health concerns and hazards regarding the safety and migration of ZnO NPs application are also elaborated. Unintentional migration, inhalation, skin penetration, and ingestion may result in human health hazards. Therefore, to provide safety regulations, further investigations such as case by case study are recommended. KEYWORDSZinc oxide nanostructure; shelf life; safety; antimicrobial activity; food packaging CONTACT Jongchul Seo

This study reveals the synthesis of spherical gold nanoparticles (Au NPs) using aqueous fruit extract of Terminalia arjuna, which contains tannin, terpenoid, saponins, flavonoids, glycosides and polyphenolic compounds. The synthesized Au NPs were characterized by UV-visible spectroscopy (UV-vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential (ZP) analyses. UV-visible spectra of the fruit extract containing Au NPs showed a surface plasmon resonance peak at 523 nm. FTIR analysis was performed to analyze the biomolecules responsible for the reduction of Au NPs. FTIR analysis clearly showed that Au NPs were capped with plant compounds. The EDX analysis was used to identify the elemental composition of the synthesized Au NPs. The high crystallinity of Au NPs with a face-centered cubic phase is evident to XRD patterns. AFM and TEM observations revealed that synthesized Au NPs were spherical shape with the range 20-50 nm. DLS measurement revealed that Au NPs were obtained in the average size of 25 nm and it is found to be stable at 21.9 mV through ZP analysis. The synthesized Au NPs were investigated for its antibacterial activity. By contrast, Au NPs did not show any antibacterial activity against Gram-positive and Gram-negative bacteria. The Au NPs were treated with two different concentrations (500 and 1,000 lM) of Gloriosa superba seeds. Au NPs exposure at 1,000 lM concentration has most significant effect on seed germination rate and vegetative growth of G. superba. This is the first report on Au NPs as a biocompatibility material to enhance the seed yield of this endangered medicinal plant. Keywords Terminalia arjuna Á Fruit extract Á Gold nanoparticles Á Gloriosa superba Á Seed germination index Electronic supplementary material The online version of this article (

Cerium oxide nanoparticles (CeO 2 NPs) were synthesized using Aspergillus niger culture filtrate. The mycosynthesized CeO 2 NPs were characterized by UVVisible (UV-Vis), Fourier Transform Infrared (FT-IR), X-ray diffraction (XRD), Micro Raman, Thermogravimetric/Differential Thermal Analysis (TG/DTA), Photoluminescence, and Transmission Electron Microscopy (TEM) analyses. UV-Vis spectrum exhibited a corresponding absorption peak for CeO 2 NPs at 296 nm, and the functional groups present in the fungal filtrate responsible for the synthesis of NPs were analyzed by FT-IR. The further characterization of the mycosynthesized CeO 2 NPs revealed particles of the cubic structure and spherical shape, with the particle sizes ranging from 5 to 20 nm. The antibacterial activity of CeO 2 NPs was examined in respect of two Gram-positive (G?) bacteria (Streptococcus pneumoniae, Bacillus subtilis) and two Gram-negative (G-) bacteria (Proteus vulgaris, Escherichia coli) by disk diffusion method. The test results for CeO 2 NPs at a concentration of 10 mg/mL showed higher activities on the zone of inhibition of up to 10.67 ± 0.33 and 10.33 ± 0.33 mm against Streptococcus pneumonia and Bacillus subtilis, respectively, The CeO 2 NPs caused 100 % mortality on first instar of Aedes aegypti at 0.250 mg/L concentration after 24-h exposure. The mycosynthesis of CeO 2 NPs is a simple, cost-effective and eco-friendly approach and it will also potentially helpful to control pathogenic bacteria and dengue vector.

A series of PLA/ZnO bionanocomposite films were prepared by introducing positively surface charged zinc oxide nanoparticles (ZnO NPs) into biodegradable poly(lactic acid) (PLA) by the solvent casting method, and their physical properties and antibacterial activities were evaluated. The physical properties and antibacterial efficiencies of the bionanocomposite films were strongly dependent on the ZnO NPs content. The bionanocomposite films with over 3% ZnO NPs exhibited a rough surface, poor dispersion, hard agglomerates, and voids, leading to a reduction in the crystallinity and morphological defects. With the increasing ZnO NPs content, the thermal stability and barrier properties of the PLA/ZnO bionanocomposite films were decreased while their hydrophobicity increased. The bionanocomposite films showed appreciable antimicrobial activity against Staphylococcus aureus and Escherichia coli. Especially, the films with over 3% of ZnO NPs exhibited a complete growth inhibition of E. coli. The strong interactions between the positively charged surface ZnO NPs and negatively charged surface of the bacterial membrane led to the production of reactive oxygen species (ROS) and eventually bacterial cell death. Consequently, these PLA/ZnO bionanocomposite films can potentially be used as a food packaging material with excellent UV protective and antibacterial properties.